Question

1. calculate the atomic mass of copper if copper - 63 is 69.17% abundant and copper - 65 is 30.83% abundant.
2. for each isotope, write in nuclide notation, and identify the number of electrons, protons, neutrons and energy levels

a. uranium - 238
b. boron - 10
c. carbon - 14

1. iodine is 80% ^{127}i, 17% ^{126}i, and 3% ^{128}i. calculate the average atomic mass of iodine.
2. the natural abundance for boron isotopes is 19.9% ^{10}b and 80.1% ^{11}b. calculate borons atomic mass.
3. hydrogen is 99% ^{1}h, 0.8% ^{2}h, and 0.2% ^{3}h. calculate its average atomic mass.

Explanation:

5.

Step1: Recall the formula for average atomic mass

The formula is $\text{Average atomic mass}=\sum_{i} (\text{Isotope mass}\times\text{Abundance})$. The mass of copper - 63 is approximately 63 amu and copper - 65 is approximately 65 amu.

Step2: Calculate the contribution of copper - 63

$63\times0.6917 = 43.5771$

Step3: Calculate the contribution of copper - 65

$65\times0.3083=20.0395$

Step4: Find the average atomic mass of copper

$43.5771 + 20.0395=63.6166\approx63.62$ amu

• Nuclide notation: Uranium has an atomic number $Z = 92$. For uranium - 238, the mass number $A=238$. The nuclide notation is $_{92}^{238}U$.
• Number of electrons: In a neutral atom, the number of electrons is equal to the atomic number. So, the number of electrons is 92.
• Number of protons: The atomic number is the number of protons. So, the number of protons is 92.
• Number of neutrons: $N=A - Z=238 - 92 = 146$.
• Energy levels: Uranium has a complex electron - configuration spread over multiple energy levels. The first few energy levels ($n = 1,2,3,\cdots$) are filled according to the Aufbau principle, Pauli exclusion principle and Hund's rule. The outermost electrons are in the $7s$ and $5f$ sub - levels.

• Nuclide notation: Boron has an atomic number $Z = 5$. For boron - 10, the mass number $A = 10$. The nuclide notation is $_{5}^{10}B$.
• Number of electrons: In a neutral atom, number of electrons=atomic number = 5.
• Number of protons: Atomic number = 5.
• Number of neutrons: $N=A - Z=10 - 5=5$.
• Energy levels: Boron's electron configuration is $1s^{2}2s^{2}2p^{1}$, with electrons in the first two energy levels ($n = 1$ and $n = 2$).

Answer:

63.62 amu

6a.